<div class="problemindexholder" problemindex="A">
 <div class="ttypography">
  <div class="problem-statement">
   <div class="header">
    <div class="title">
     A. Mister B and Book Reading
    </div>
    <div class="time-limit">
     <div class="property-title">
      time limit per test
     </div>
     2 seconds
    </div>
    <div class="memory-limit">
     <div class="property-title">
      memory limit per test
     </div>
     256 megabytes
    </div>
    <div class="input-file">
     <div class="property-title">
      input
     </div>
     standard input
    </div>
    <div class="output-file">
     <div class="property-title">
      output
     </div>
     standard output
    </div>
   </div>
   <div>
    <p>
     Mister B once received a gift: it was a book about aliens, which he started read immediately. This book had
     <span class="tex-span">
      <i>
       c
      </i>
     </span>
     pages.
    </p>
    <p>
     At first day Mister B read
     <span class="tex-span">
      <i>
       v
      </i>
      <sub class="lower-index">
       0
      </sub>
     </span>
     pages, but after that he started to speed up. Every day, starting from the second, he read
     <span class="tex-span">
      <i>
       a
      </i>
     </span>
     pages more than on the previous day (at first day he read
     <span class="tex-span">
      <i>
       v
      </i>
      <sub class="lower-index">
       0
      </sub>
     </span>
     pages, at second —
     <span class="tex-span">
      <i>
       v
      </i>
      <sub class="lower-index">
       0
      </sub>
      +
      <i>
       a
      </i>
     </span>
     pages, at third —
     <span class="tex-span">
      <i>
       v
      </i>
      <sub class="lower-index">
       0
      </sub>
      + 2
      <i>
       a
      </i>
     </span>
     pages, and so on). But Mister B is just a human, so he physically wasn't able to read more than
     <span class="tex-span">
      <i>
       v
      </i>
      <sub class="lower-index">
       1
      </sub>
     </span>
     pages per day.
    </p>
    <p>
     Also, to refresh his memory, every day, starting from the second, Mister B had to reread last
     <span class="tex-span">
      <i>
       l
      </i>
     </span>
     pages he read on the previous day. Mister B finished the book when he read the last page for the first time.
    </p>
    <p>
     Help Mister B to calculate how many days he needed to finish the book.
    </p>
   </div>
   <div class="input-specification">
    <div class="section-title">
     Input
    </div>
    <p>
     First and only line contains five space-separated integers:
     <span class="tex-span">
      <i>
       c
      </i>
     </span>
     ,
     <span class="tex-span">
      <i>
       v
      </i>
      <sub class="lower-index">
       0
      </sub>
     </span>
     ,
     <span class="tex-span">
      <i>
       v
      </i>
      <sub class="lower-index">
       1
      </sub>
     </span>
     ,
     <span class="tex-span">
      <i>
       a
      </i>
     </span>
     and
     <span class="tex-span">
      <i>
       l
      </i>
     </span>
     (
     <span class="tex-span">
      1 ≤
      <i>
       c
      </i>
      ≤ 1000
     </span>
     ,
     <span class="tex-span">
      0 ≤
      <i>
       l
      </i>
      &lt;
      <i>
       v
      </i>
      <sub class="lower-index">
       0
      </sub>
      ≤
      <i>
       v
      </i>
      <sub class="lower-index">
       1
      </sub>
      ≤ 1000
     </span>
     ,
     <span class="tex-span">
      0 ≤
      <i>
       a
      </i>
      ≤ 1000
     </span>
     ) — the length of the book in pages, the initial reading speed, the maximum reading speed, the acceleration in reading speed and the number of pages for rereading.
    </p>
   </div>
   <div class="output-specification">
    <div class="section-title">
     Output
    </div>
    <p>
     Print one integer — the number of days Mister B needed to finish the book.
    </p>
   </div>
   <div class="sample-tests">
    <div class="section-title">
     Examples
    </div>
    <div class="sample-test">
     <div class="input">
      <div class="title">
       Input
      </div>
      <pre>5 5 10 5 4<br/></pre>
     </div>
     <div class="output">
      <div class="title">
       Output
      </div>
      <pre>1<br/></pre>
     </div>
     <div class="input">
      <div class="title">
       Input
      </div>
      <pre>12 4 12 4 1<br/></pre>
     </div>
     <div class="output">
      <div class="title">
       Output
      </div>
      <pre>3<br/></pre>
     </div>
     <div class="input">
      <div class="title">
       Input
      </div>
      <pre>15 1 100 0 0<br/></pre>
     </div>
     <div class="output">
      <div class="title">
       Output
      </div>
      <pre>15<br/></pre>
     </div>
    </div>
   </div>
   <div class="note">
    <div class="section-title">
     Note
    </div>
    <p>
     In the first sample test the book contains
     <span class="tex-span">
      5
     </span>
     pages, so Mister B read it right at the first day.
    </p>
    <p>
     In the second sample test at first day Mister B read pages number
     <span class="tex-span">
      1 - 4
     </span>
     , at second day —
     <span class="tex-span">
      4 - 11
     </span>
     , at third day —
     <span class="tex-span">
      11 - 12
     </span>
     and finished the book.
    </p>
    <p>
     In third sample test every day Mister B read
     <span class="tex-span">
      1
     </span>
     page of the book, so he finished in 15 days.
    </p>
   </div>
  </div>
  <p>
  </p>
 </div>
</div>
